Drum Printer

Drum printers were a type of very fast impact line printer. The
entire character set is engraved on the outside of a metal drum,
for every column of print. As the drum spins, a hammer strikes
through the paper and ink ribbon, timed to hit the correct character
as it comes around on the rotating drum. In this way, an entire line
of text can be printed simultaneously, in the time it takes for
the drum to rotate once. (In practice, many drum printers (this
one included) actually have a hammer for every other spot, so
it take two passes to print one line.)